This invention relates, in general, to electroluminescent systems, and more specifically to a membranous electroluminescent structure comprising an electroluminescent system encapsulated in a UV-cured urethane envelope.
An embodiment of the invention taught by related application Ser. No. 09/173,521 is directed to an electroluminescent (xe2x80x9cELxe2x80x9d) system having a unitary carrier whose layers form a monolithic structure. A preferred unitary carrier in this system is a vinyl resin. One of the advantages of this monolithic electroluminescent system is that the layers thereof may be deployed as inks onto a wide variety of substrates using screen printing or other suitable methods. The disclosure of Ser. No. 09/173,521 is incorporated herein by reference.
This vinyl-based monolithic structure is also disclosed in an exemplary embodiment of the membranous electroluminescent devices taught by related application Ser. No. 09/173,404. Specifically, Ser. No. 09/173,404 teaches exemplary use of the vinyl-based monolithic structure as an electroluminescent laminate deployed between two membranous urethane envelope layers. The disclosure of Ser. No. 09/173,404 is incorporated herein by reference.
While the electroluminescent systems described in Ser. Nos. 09/173,521 and 09/173,404 have been found to be serviceable, it will be appreciated that yet further advantages of monolithic structure will be obtained if the electroluminescent laminate in Ser. No. 09/173,404 had layers suspended in a urethane carrier. In this way, the membranous electroluminescent devices disclosed in Ser. No. 09/173,404 would comprise layers in the electroluminescent laminate that were in monolithic unity with surrounding urethane envelope layers. Co-pending, concurrently-filed patent application MEMBRANOUS MONOLITHIC EL STRUCTURE WITH URETHANE CARRIER, Ser. No. 09/974,918, addresses this need by providing, in an exemplary embodiment, a membranous monolithic urethane electroluminescent structure whose monolithic phase comprises a series of contiguous electroluminescent layers deployed using a unitary vinyl gel resin carrier that is catalyzed to transform into a unitary urethane carrier during curing. The disclosure of MEMBRANOUS MONOLITHIC EL SYSTEM WITH URETHANE CARRIER, Ser. No. 09/974,918, is incorporated herein by reference.
Regardless of whether the layers of the electroluminescent system cure to a vinyl or urethane (or any other polymer), however, the surrounding membranous envelope layers have been heat cured up until now. Typically, in the membranous lamp disclosed in application Ser. No. 09/173,404, a heat cure of about 105xc2x0 C. for about 35 minutes per deployed urethane envelope layer is required. In a structure having envelope layer thickness built up from several individual urethane layer deployments, the curing phase now requires multiples of 35-minute cures, thereby adding significantly to the manufacturing cycle time (and cost) for the structure.
Moreover, heat curing has been found to cause shrinkage of the height of individually deployed layers. Thus, even more layers are required to be deployed to build up an overall envelope layer height, extending the manufacturing cycle time for curing even further.
There is therefore a need in the art for an alternative to heat curing the envelope layers in a membranous EL structure. Advantageously, such an alternative will not only reduce curing cycle times, but also minimize individual deployed layer height shrinkage.
The present invention addresses the above-described problems by curing the envelope layers in a membranous EL structure using ultra-violet (xe2x80x9cUVxe2x80x9d) radiation. In a presently preferred embodiment, the envelope layers comprise a UV-curable ink such as a urethane acrylate/acrylate monomer. When deployed in layer form and exposed to UV radiation, the ink cures in a few seconds without any appreciable layer height shrinkage. Manufacturing cycle time is significantly optimized over traditional heat curing processes. The resulting membranous UV-cured EL structure nonetheless has all the advantages of membranous EL structures as disclosed in application Ser. No. 09/173,404 and co-pending concurrently-filed application Ser. No. 09/974,918.
The reduction of curing cycle times for individually deployed layers from minutes to seconds further enables manufacturing to convert from a batch curing system to a continuous curing system. A preferred embodiment of the present invention may be cured on a UV curing conveyor system as is well known in the art. This is in distinction to heat curing xe2x80x9cbatchesxe2x80x9d of EL structures layer by layer in an oven, as is generally undertaken in current manufacturing. Further optimization of manufacturing cycle time results. Not only is there a reduction in curing cycle time because each envelope layer now cures in seconds rather than minutes, there is also an optimization of handling time through use of a continuous system.
Accordingly, a technical advantage of the present invention is that curing cycle times for the inventive membranous envelope inks are dramatically reduced.
A further technical advantage of the present invention is that deployed layer height shrinkage is also reduced. As a result, fewer individually deployed layers are necessary to achieve a desired overall membranous envelope layer thickness.
A further technical advantage of the present invention is that continuous curing techniques are now available to manufacturing processes, in contrast to the batch techniques that are currently available.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.